More often, the factors that cause motor vibration are a comprehensive problem. Excluding the influence of external factors, the bearing lubrication system, rotor structure and balance system, structural parts strength, and electromagnetic balance in the motor manufacturing process are the key to vibration control. Ensuring the low vibration of the motor produced is an important condition for the quality competition of the motor in the future.

1. Reasons for the lubrication system

Good lubrication is a necessary guarantee for the operation of the motor. During the production and use of the motor, it should be ensured that the grade, quality and cleanliness of the grease (oil) meet the requirements, otherwise it will cause the motor to vibrate and have a serious impact on the life of the motor.

For a bearing pad motor, if the bearing pad clearance is too large, the oil film cannot be established. The bearing pad clearance must be adjusted to the proper value. For a motor that has been out of use for a long time, check whether the oil quality meets the standard and whether there is a lack of oil before putting it into operation. For a forced-lubricated motor, check whether the oil circuit system is blocked, whether the oil temperature is appropriate, and whether the circulating oil volume meets the requirements before starting. The motor should be started after the test run is normal.

2. Mechanical failure

●Due to long-term wear and tear, the bearing clearance is too large during the operation of the motor. The replacement grease should be added periodically, and new bearings should be replaced if necessary.

The rotor is unbalanced; this kind of problem is rare, and the dynamic balance problem has been solved when the motor leaves the factory. However, if there are problems such as loosening or falling off of the fixed balance sheet during the dynamic balancing process of the rotor, there will be obvious vibration. This will cause damage to the sweep and windings.

●The shaft is deflected. This problem is more common for rotors with short iron cores, large diameters, extra long shafts and high rotational speeds. This is also a problem that the design process should try to avoid.

●The iron core is deformed or press-fitted. This problem can generally be found in the factory test of the motor. In most cases, the motor shows a friction sound similar to the sound of insulating paper during operation, which is mainly caused by the loose iron core stacking and the poor dipping effect.

●The fan is unbalanced. Theoretically, as long as the fan itself has no defects, there will not be too many problems, but if the fan has not been statically balanced, and the motor has not been subjected to the final vibration inspection test when it leaves the factory, there may be problems when the motor is running; another The situation is that when the motor is running, the fan is deformed and unbalanced due to other reasons such as motor heating. Or foreign objects have fallen between the fan and the hood or end cover.

●The air gap between stator and rotor is uneven. When the unevenness of the air gap between the stator and rotor of the motor exceeds the standard, due to the action of the unilateral magnetic pull, the motor will vibrate at the same time that the motor has serious low-frequency electromagnetic sound.

●Vibration caused by friction. When the motor starts or stops, friction occurs between the rotating part and the stationary part, which also causes the motor to vibrate. Especially when the motor is not properly protected and foreign objects enter the inner cavity of the motor, the situation will be more serious

3. Electromagnetic failure

In addition to mechanical and lubrication system problems, electromagnetic problems can also cause vibration in the motor.

●The three-phase voltage of the power supply is unbalanced. The motor standard stipulates that the general voltage fluctuation shall not exceed -5%~+10%, and the three-phase voltage unbalance shall not exceed 5%. If the three-phase voltage unbalance exceeds 5%, try to eliminate the unbalance. For different motors, the sensitivity to voltage is different.

●Three-phase motor is running without phase. Problems such as power lines, control equipment, and the terminal wiring in the motor junction box are blown due to poor tightening, which will cause the motor input voltage to be unbalanced and cause different degrees of vibration problems.

● Three-phase current uneven problem. When the motor has problems such as uneven input voltage, short circuit between turns of the stator winding, wrong connection of the first and last ends of the winding, unequal number of turns of the stator winding, wrong wiring of some coils of the stator winding, etc., the motor will vibrate obviously, and it will be accompanied by serious dullness. Sound, some motors will spin in place after being powered on.

●The impedance of the three-phase winding is uneven. This kind of problem belongs to the rotor problem of the motor, including serious thin strips and broken strips of the cast aluminum rotor, poor welding of the wound rotor, and broken windings.

●Typical inter-turn, inter-phase and ground problems. This is an inevitable electrical failure of the winding part during the operation of the motor, which is a fatal problem for the motor. When the motor vibrates, it will be accompanied by serious noise and burning.

4. Connection, transmission and installation problems

When the strength of the motor installation foundation is low, the installation foundation surface is inclined and uneven, the fixing is unstable or the anchor screws are loose, the motor will vibrate and even cause the motor feet to break.

The transmission of motor and equipment is driven by pulley or coupling. When the pulley is eccentric, the coupling is improperly assembled or loose, it will cause the motor to vibrate to different degrees.